Information recording medium and tracking error signal detection apparatus and magnetic recording apparatus and method of adjusting the magnetic recording apparatus

Abstract

In a magnetic recording medium to detect tracking error signals optically where an optical head and a magnetic head scan different tracks, two signals having phases different by π/2 are generated and added or subtracted. By changing the amplitude of the two signals with a changeable gain amplifying means, a phase of a tracking error signal is changed so that the servo operation is conducted at the middle of the amplitude of the tracking error signal to keep the magnetic head on track.

What is claimed is: 
     
       1. A tracking error signal detection apparatus comprising a light source to radiate a light beam, a beam generating means to generate three beams from the light beam radiated from the light source, a converging optical system to converge the three light beams radiated from the light source on a reflecting body in minute spots, a beam splitting means to split the three light beams reflected and diffracted by the reflecting body, a photodetector having three sensing portions to sense the beam splitted by the beam splitting means and output signals according to the quantity of light, first and second changeable gain amplifying means to change the intensity of the signals outputted from the first and second sensing portions of the photodetector, third and fourth changeable gain amplifying means to change the intensity of the signals outputted from the second and third sensing portions of the photodetector, a first differential operation means to subtract the signals outputted from the first and second changeable gain amplifying means, a second differential operation means to subtract the signals outputted from the third and fourth changeable gain amplifying means, fifth and sixth changeable gain amplifying means to change the intensity of the signals outputted from the first and second differential operation means, and an operation means to add Or subtract the signals outputted from the fifth and sixth changeable gain amplifying means. 
     
     
       2. The tracking error signal detection apparatus according to claim 1, wherein the gain of the changeable gain amplifying means is adjusted so that a DC component outputted from the differential operation means becomes zero. 
     
     
       3. The tracking error signal detection apparatus according to claim 1, wherein the gain of the changeable gain amplifying means is adjusted so that a signal outputted to a means to read out the information recorded on the information recording medium becomes maximum. 
     
     
       4. The tracking error signal detection apparatus according to claim 1, wherein the converging optical system comprises a collimator to convert a divergent beam radiated from the light source to a parallel light beam, and a converging lens to convert the parallel light beam converted by the collimator to a convergent light beam. 
     
     
       5. The tracking error signal detection apparatus according to claim 1, wherein the converging optical system comprises a finite object lens to convert a divergent light beam radiated from the light source to a convergent light beam. 
     
     
       6. The tracking error signal detection apparatus according to claim 1, wherein the converging optical system is formed by molding a plastic. 
     
     
       7. The tracking error signal detection apparatus according to claim 1, wherein the beam splitting means is a diffraction element. 
     
     
       8. The tracking error signal detection apparatus according to claim 1, wherein the beam splitting means is a polarizing beam splitter. 
     
     
       9. The tracking error signal detection apparatus according to claim 1, wherein the reflecting body is an information recording medium.